1. Field of the Invention
The present invention relates to an ink jet recording head for forming images and the like on a recording medium, and a method of manufacture therefor. More particularly, the invention relates to a method for forming the discharge ports of an ink jet recording head.
2. Related Background Art
Conventionally, as one of the methods for forming discharge ports of an ink jet recording head, there has been known the one in which openings are made by means of laser processing on the grooved ceiling plate from behind the flow paths, which is the so-called grooved ceiling plate integrally formed with an orifice plate, having the grooves to from ink flow paths, as well as the discharge port forming member (the orifice plate) for forming the discharge ports in front of those grooves, respectively.
When the drilling of the kind is performed from behind the flow paths, laser beams are kicked by the grooves of the grooved ceiling plate, which makes it impossible to effectuate incidence from right behind (at the drilling angle of 0xc2x0). The drilling is, therefore, performed at an angle of approximately 10xc2x0, and the resultant angle of each hole formed on the orifice plate is approximately 10xc2x0 to the flow paths.
FIG. 9 is a view which schematically shows the example of the conventional laser processing. In FIG. 9, a reference numeral 1 designates a nozzle drilled by the laser processing; 1a, a discharge port on the outer end of the nozzle 1; 2, a flow path to supply ink; 3, an orifice plate where drilling is made; 4, a grooved ceiling plate; 5, laser processing surface; 6, laser beam; and 7, a heater (heat generating element). As shown in FIG. 1, the laser incident angle is usually 10xc2x0xc2x11xc2x0 approximately.
However, with a certain angle of a hole to the flow path as described above in a series of operations, such as supplying ink from the common liquid chamber to a flow path, and then, enabling ink to fly out of the discharge port through the hole (flow path) formed by the laser processing, the direction of the flow rate vector of liquid is caused to change on the way to create subtle disturbance of liquid flow. As a result, the flow rate vector collides with the flow path walls to make the orientation unstable when ink is discharged to fly from each discharge port. Not only the discharge energy is dispersed, but also, the flying directions of the main droplet and its satellites are caused to differ eventually.
Under the circumstances, the main droplet and its satellites are impacted on different positions on a recording medium when an image is formed on the recording medium, hence disturbing the recorded image. Also, when the reciprocal printing is performed by use of a serial printer or the like, the flying direction of liquid droplets is not perpendicular to a recording medium from the outset, because the flow path axis is not orthogonal to the orifice plate surface. Further, the distance between impacted dots is caused to change at the time of xe2x80x9cforwardxe2x80x9d and xe2x80x9cbackwardxe2x80x9d operations, which may also bring about the uneven density.
In addition, the distance between the head and the recording medium (the flying distance of ink) is caused to change delicately by cockling of the recording medium to be carried. As a result, the impacted positions of the main and satellite droplets may also change to cause uneven density.
It is an object of the present invention to provide an ink jet recording head capable of enhancing the overall image quality by eliminating the deviation in flying directions of the main droplet and satellites due to the inclined axis of discharge, and the instability of discharge directions and discharging power, as well as by improving image unevenness on the forward and backward printing among some others. The invention is also aimed at providing a method for manufacturing such ink jet recording head.
In this respect, the applicant hereof has filed an application (Japanese Patent Laid-Open Application 10-13980) for various patents that include means for controlling drilling angles and the like by adjusting the amount of light transmission by use of gradient mask in order to shield laser beams locally or stepwise. The aforesaid means is the one whereby to control the drilling angles effectively just by forming adjustment patterns for the amount of light transmitted to a drilling mask. With this means, the drilling angle is made considerably close to the horizontal as compared with the conventional art, thus enhancing the stability of discharge direction. It is another object of the present invention to improve the invention disclosed in the specification of the previous application.
More specifically, with respect to the means that uses gradient mask, the patterns of gradient portion are changed one to one in accordance with the parameters of the thickness or the hole area of an orifice plate if changed any, and if the nozzle design may change, it should also change accordingly. Here, there is automatically a limit to the pattern that may be incorporated with one mask. Therefore, should a number of patterns exceed such limit, the masks are exchanged. Also, if laser processing should be required to be performed for a plurality of blocks which are divided for the formation of the grooved ceiling plate to be used for an elongated line head, the mask pattern exchange performance is included in the drilling sequence in order to obtain the same hole configurations between the processing blocks, because the thickness of an orifice plate may delicately change depending on a drilling block.
In other words, it is still another object of the present invention to provide an excellent ink jet recording head capable of performing vertical discharges as described above, which can be manufactured more simply and efficiently, as well as to provide the method of manufacture therefor. With this method, it becomes possible to obtain uniform shape and area of each hole particularly for an elongated head or the like, and also, to reduce the designing load with simpler process procedures. The invention is also aimed at providing the method for manufacturing such ink jet recording head.
It is a further object of the invention to provide a method for manufacturing an ink jet recording head, which is provided with a first base plate having energy generating elements for generating energy utilized for discharging ink, and a second base plate bonded to the first base plate which has grooves for forming ink flow paths corresponding to said energy generating elements, and discharge port forming member for forming discharge ports for discharging said ink integrally formed in front of the grooves, comprises the steps of forming the discharge ports by drilling the discharge port forming member with the reflecting light of laser beams reflected from the groove wall faces of the second substrate, and the direct light of laser beams on the discharge port forming member; and forming the flow paths by bonding the first base plate and the second base plate with the grooves inside.
In accordance with the invention thus structured, the nozzles capable of performing vertical discharges can be materialized by the system which is simpler than the conventional one. Then, it is made possible to overcome the long standing difficulty for the grooved ceiling plate (the ceiling plate integrally formed with the orifice plate) that deviation may occur in the flying directions of the main droplet and its satellites due to the inclined discharge axis, and that the discharge direction and discharging power may become instable. Hence, the overall image quality can be enhanced by improving the image unevenness that may be brought about by the forward and backward printing.